In the Garden:New England
May, 2006
Regional Report

Slug alert: This is apt to be the biggest pest in your garden this year.

What's Bugging You?

Because of the mild winter and soaking spring, it promises to be a banner year for garden pests. I'm bracing myself for the onslaught. The slugs are rearing their ugly heads already, so I've been wearing thick-soled shoes whenever I visit my garden and outdoor containers. Fortunately there are effective home remedies, and more non-toxic commercial products than ever before for dealing with pests.

Slugs
Before you head out to the garden, make yourself a pot of coffee. But don't sit down and relax, take the pot outside and pour the coffee on the ground. No, this isn't some weird ritual to ward off evil spirits, it's a ritual to ward off evil mollusks. USDA researchers in Hilo, Hawaii, have found that caffeinated coffee kills or repels slugs and snails better than the commercial slug bait, metaldehyde. The higher the caffeine content, the better. Even coffee grounds will repel slugs, but the liquid coffee appears to be more effective.

A better-known trap for slugs also comes from the kitchen: beer. I've had mixed success with this, but the idea is to fill shallow containers with stale beer and submerge them up to the rims in the soil. The unsuspecting slugs are attracted to the beer, crawl in, and drown. These traps need to be checked daily because they fill up quickly with debris, and the beer gets watered down after a rain.

Iron phosphate baits are another option, and diatomaceous earth is a non-toxic powder that kills slugs as they crawl over it. A good barrier method is to surround plants with copper strips made for this purpose. They truly give slugs a shock on contact.

Caterpillars
For caterpillars on trees, shrubs, and vegetable crops, it's hard to beat the benign bacterial insecticide Bacillus thuringiensis. Spray it on and reapply after a rain.

Veggies are easy to protect with lightweight row covers. They prevent visits from flying insects that would love to lay eggs on your plants.

Rose Slugs
These tiny, light green larvae decimate rose leaves. They are the larvae of sawflies and look like caterpillars but they aren't, so Bt doesn't help. A summer horticultural oil spray is effective, as is a relatively new organic insecticide called Spinosad. It controls a range of insects, such as cabbage loopers, leafminers, armyworms, some beetles (although not Japanese beetles). Both sprays need to be used when insects are present, not as preventatives.

Japanese Beetles
Neem spray is a botanical control for Japanese beetles that can be used on many types of plants. Insecticidal soap sprays also work. For fruit crops, you can use Surround, a spray of kaolin clay that coats the plant with a white film that makes the plants unappealing to the beetles (and unattractive to some gardeners, as well).

My favorite method is to visit plants late in the evening or early morning when they are sluggish and knock them into a can of soapy water. Very satisfying!

Another idea is to plant a trap crop that will attract beetles and presumably keep them off your favorite plants. Japanese beetles are very fond of good old garden geraniums (especially white ones, says one friend), and when they feed they are paralyzed, even killed, by a chemical in the plant. So try setting some pots of geraniums around to lure the beetles.

Getting rid of Japanese beetle larvae is also a good plan of attack, and two non-toxic controls are milky spore and beneficial nematodes. But milky spore doesn't work well in cooler regions like New England, and I've read that beneficial nematodes aren't very effective in clay or sandy soils. If you have a nice loam, give them a try (lucky you!).

Kitchen Sprays
Capsaicin, the active ingredient in chili peppers, repels mites, aphids, whiteflies, and many other insects. Mix a few tablespoons of hot pepper sauce in 1 gallon of water, add a tablespoon of liquid soap to help it stick to foliage, and spray. Keep it away from plants that chipmunks and squirrels might visit because it can injure them.

Garlic spray also works. Crush a whole bulb in 1 gallon of water, strain, and spray. It's worth testing any spray on a few leaves first to make sure it doesn't burn the foliage.

With any method of controlling pests, visiting the garden often to spot damage early is the key to success.